The Learning Center

What are Data Packets?

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When you send an email, read a news story on your computer or shop online, you're sending information and getting information digitally, or electronically. It make look like you're sending a whole photo of your new poodle to Aunt Jane and Uncle Louie across country, but it's actually a collection of electronic data, in small pieces.

A new concept? Not at all. Samuel Morse, for whom Morse code is named, sent the first telegraphic, and digital, message in 1838. Not 1938...1838!

Morse used a series or dots and dashes to make letters, then words and sentences. But those were just electronic impulses that registered as noises. Zoom ahead to today (2014) and digital communications rule the day once more. But instead of messages that need to be captured and interpreted by humans, digital information is sent, received, "unscrambled" and presented on our computer screens for us to view, read and hear.

And the innovation that makes it all possible is something called the digital "packet." The networking protocols (TCP/IP) divide your message into small digital packets and send them out onto the Internet. When your packetized message arrives at its intended destination (such as a Website), TCP/IP on the receiving end reassembles the packets into your original message.

Let's look at the seven key points in a data transmission you might make—such as sending an email or making an Internet query to find a website—and see how packets play a role the entire time.

  1. A packet isn't information or data itself: as the name suggest, it contains or encloses the actual information that's traveling to another computer. But its value is in more than bundling data into a message; packets also have the ability to do the following:
    • Addressing
    • Error correction
    • Using multiple pathways to send the data
    • Organizing the data according to its data type, such as a frame, segment, or block
    Of course, the packet that matters the most for us is an Internet packet: when you send a request for information from a website, for instance.
  2. First, your computer creates a packet, organized in a very specific way that the receiving computer can understand and use. This entire packet or "stream of data" is broken down to a specific number of "bytes" (eight bits of zeros or ones), which are individual packets that are part of the big data packet. Each packet holds about 1,000 to 1,500 bytes.
  3. The packet has a "header"; to the packet, your computer adds the IP address of the computer that your data is supposed to get to, and puts your IP address on it to.
  4. Your computer adds two identifying numbers to each of the smaller packets. The first number represents the number of packets that all of the information is divided into. The second number represents the number of each individual packet among the total sequence of packets.
  5. Your computer's internal networking hardware and software follow guidelines for bundling the data that you're sending out...the "payload." Those guidelines are spelled out in the Transmission Control Protocol/Internet Protocol (TCP/IP).
  6. Each packet also has a trailer or footer, which contains a few electronic bits that tell the receiving computer when its reached the end of the packet sequence. It also might include the results of a Cyclic Redundancy Check (CRC). The CRC contains the sum of all the "1s" in the packet, added up by your computer. The receiving also does the same math, and if the math doesn't add up, it may ask your computer to retransmit the packet.
  7. Your computer sends each packet onto the Internet separately, and each packet takes the best route available at the time when it can go. Why does it happen this way? So that the network can spread data traffic evenly, and all your data won't get stuck or slowed down in one spot. (Keep in mind, a traffic jam might only last a fraction of a second.)

What's absolutely amazing about all this is the speed in which all this takes place...mere seconds.

When you open an application on your computer (host), such as an email program, and you compose a note and click on "send," digital packets immediately travel through your computer, across network cables thousands of miles long, into the receiving computer/server, and into the appropriate program for translation. And the same happens in reverse just as fast.

Mr. Morse would be impressed.